UNDERSTANDING THE PRINCIPLE OF TESTICULAR ASCENT
HOW DOES TESTICULAR ASCENT THERMAL CONTRACEPTION (TATC) WORK?
This method involves increasing the temperature of the testicles — usually between 33 and 35 °C in the scrotum — by using body heat. By mechanically raising the testicles inside the body, their temperature can be brought closer to that of the rest of the body, around 37 °C. This slight increase in temperature can be enough to reversibly alter sperm production.
Clinical trials conducted at Toulouse University Hospital showed that if the testicles are maintained in this position for 15 hours per 24-hour period, the sperm count can decrease sufficiently to render the semen infertile.
It is therefore a non-hormonal, non-invasive, and reversible method of contraception.
To learn more, visit our page on thermal contraception.
WHO IS THE CTRT FOR?
TRCC is indicated for all people over 18 years of age who have testicles and are fertile, who have sexual intercourse with partners who have ovaries and are fertile, and who do not wish for these sexual encounters to lead to pregnancy.
It should not be used by people with contraindications (see dedicated question in the FAQ).
WHAT ARE THE DEVICES AVAILABLE TO SET UP A CTRT TODAY?
Today, no medical device is authorized by health authorities for testicular ascent thermal contraception (TATC).
In practice, users resort to artisanal devices—silicone rings, adapted underwear, jockstraps—whose manufacture and use are passed on during workshops organized by collectives and associations in different cities.
A silicone ring, the AndroSwitch, marketed as a contraceptive in 2018, helped popularize the method before its sale was discontinued in 2021 at the request of the ANSM, due to a lack of CE marking.
Today, the dissemination of these practices relies mainly on associative networks and user communities.
See the map of associations and collectives or book an individual appointment with Otoko.
DO HEATED UNDERWEAR WARM YOU UP?
The term "heated brief" is sometimes used to describe the thermal contraception device developed by Dr. Mieusset at Toulouse University Hospital. This term is misleading: the device holds the testicles in a high position, thus naturally placing them in a warmer area of the body, at around 37°C, whereas their temperature is usually between 33°C and 35°C in the scrotum.
It is this increase in temperature that can inhibit sperm production, but there is no external heat input.
WHY THE TEMPERATURE OF 37°C?
37°C is the average internal temperature of the human body. By retracting the testicles, it is possible to increase their temperature without using an external heat source.
Several studies have shown that this temperature increase can be sufficient to lower a user's sperm concentration below the 1 M/ml threshold, which guarantees contraceptive effectiveness.
IS IT PAINFUL, UNCOMFORTABLE, OR RISKY?
Testicular retraction may require a short period of adaptation, but it should not be painful in any way. Users recommend starting with testicular retraction for a few hours on the first few days, and gradually increasing the duration to reach 15 hours/day after one week. Within a maximum of 2 weeks, you will be perfectly accustomed to the new position of your testicles.
DOES THERMAL CONTRACEPTION PROTECT AGAINST STIs/STDs?
Thermal contraception does not protect against STDs/STIs.
In risky situations, the use of a condom remains necessary.
HOW TO IMPLEMENT THERMAL CONTRACEPTION?
Before implementing thermal contraception, it is important to be well informed about this method.
Numerous scientific and educational resources are available online, particularly on our bibliography page, which gathers publications and reference documents on male thermal contraception.
We also recommend getting in touch with associations or collectives that support users of thermal contraception. These organizations can provide practical information, share experiences, and help better understand the implementation of the method.
Finally, it is highly recommended to be accompanied by a healthcare professional in order to benefit from appropriate follow-up.
You can consult the map of male contraception stakeholders to identify associations, collectives, and healthcare professionals who can support you.
HOW TO PERFORM A SPERMOGRAM AND WHERE?
A spermogram should be performed in a medical analysis laboratory or a specialized hospital department.
The prescribing doctor generally indicates the most suitable and closest location to you. Otherwise, you can find addresses of laboratories that perform spermograms on Doctolib or on the map of male contraception actors.
Home-based self-tests are currently under development.
EFFECTIVENESS/SAFETY OF THERMAL CONTRACEPTION
HOW LONG DOES IT TAKE FOR THE METHOD TO BE EFFECTIVE?
Sperm is stored in the vas deferens for up to 3 months after production. For this reason, it can take between 2 and 4 months to achieve contraceptive efficacy with the testicular ascent thermal contraception method. In the event of sexual intercourse with a risk of conception, another method of contraception must be used until efficacy is confirmed. A spermogram is performed at 3 months (then monthly if the contraceptive threshold is not reached). Contraceptive efficacy is considered confirmed when sperm concentration is less than 1 million/mL in two successive spermograms performed three weeks apart.
As long as contraceptive efficacy has not been confirmed by a spermogram, the user cannot consider themselves to be contracepted.
HOW LONG DOES IT TAKE TO REGAIN NORMAL FERTILITY AFTER STOPPING THE METHOD?
Contraceptive effectiveness is no longer guaranteed once the method is discontinued.
Even if pregnancy is desired, another method of contraception should be used immediately after the device is removed and for at least 6 months, which corresponds to two spermatogenesis cycles, as a precautionary measure.
The complementary contraceptive method can be discontinued after 6 months, once a spermogram has confirmed the return to fertility.
ARE THERE ANY KNOWN SIDE EFFECTS OF THE METHOD?
With the artisanal devices used until now, reported side effects of TRCT vary from person to person. These effects may include: decreased testicular volume, temporary skin irritation, itching, fungal infections, decreased testicular size, testicular discomfort, unpleasant erections, and post-void dribbling. No life-threatening risks have been reported.
CAN TESTICULAR ASCENT CAUSE TESTICULAR CANCER?
The question is regularly asked because it has been shown that people with a history of cryptorchidism (failure of at least one testicle to descend into the scrotum in a young boy) have a higher probability of developing testicular cancer during their lifetime.
Today, however, several publications on the subject seem to show that body heat applied to a testicle does not increase the risk of cancer.
According to the literature, the genesis of testicular cancer primarily occurs during fetal life with underlying genetic/epigenetic predispositions and interactions with endocrine disruptors, leading to Skakkebaek's hypothesis.
In particular, the following publications support this hypothesis and seem to rule out the impact of body heat on testicular cancer:
.< "Adolescent and adult risk factors for testicular cancer", published in Nature Reviews Urology, 2012
.< "Risk Factors for Testicular Cancer: Environment, Genes and Infections—Is It All?" published in Medicina, 2023
More studies will need to be conducted on this subject in the future.
As a precautionary principle, the use of thermal contraception is not recommended for people with a history of cryptorchidism or testicular cancer.
CAN TESTICULAR RETRACTION DECREASE MY TESTOSTERONE LEVEL?
During the clinical trials conducted by Dr. Mieusset at the Toulouse University Hospital, no effect on testosterone levels was observed for 15 hours of exposure per day.
However, for 24 hours of exposure per day, a decrease in testosterone levels was observed in Dr. Shafik's study, "Testicular suspension as a method of male contraception: technique and results," although all individual values remained within normal limits, and initial values were restored after discontinuation.
This point will be the subject of clinical investigation by 37 degrees as part of the CE marking project for the contraceptive device.
CAN CTRT BE USED CONTINUOUSLY FOR SEVERAL YEARS?
Yes, if the method is well tolerated. Like any contraception, it is part of regular medical monitoring.
Patients were followed for up to 4 years of wearing during clinical trials conducted at Toulouse University Hospital by Dr. Mieusset.
WHEN SHOULD YOU USE DOUBLE CONTRACEPTION?
The contraception threshold – sperm concentration below 1 M/ml – is reached after 3 to 6 months of CTRT use. It is therefore recommended to use a second form of contraception when starting CTRT, as well as after a missed dose or prolonged interruption, or when stopping CTRT, before returning to initial fertility if there is a desire for children, for example.
MUST A PHYSICIAN SUPERVISE OR APPROVE THE USE OF THE DEVICE?
Medical follow-up is recommended for the implementation and monitoring of this contraceptive method, in particular to check for contraindications and to monitor contraceptive effectiveness in the long term.
WHAT TYPES OF MEDICAL TESTS ARE REQUIRED BEFORE USING THE DEVICE?
A consultation with a doctor and a spermogram are necessary before starting CTRT to ensure it is effective and efficient. Additional follow-up appointments are required to monitor contraceptive efficacy.
ARE THERE ANY CONTRAINDICATIONS OR PROFILES FOR WHICH THIS METHOD IS NOT SUITABLE?
Pending further studies, CTRT is not recommended in the following cases as a precaution: history of abnormal testicular descent (cryptorchidism, ectopy, treated or not); grade 3 varicocele on clinical examination; history of inguinal hernia (treated or not); testicular cancer; history of testicular torsion with unilateral or bilateral orchiopexy (AE).
CTRT is discussed in cases of: sperm abnormality (oligozoospermia: sperm concentration < 15 million/ml; asthenozoospermia: progressive motility < 32%; teratozoospermia: normal forms < 4% according to Kruger or < 24% according to the modified David classification); obesity: exclusion criterion for efficacy studies, potentially difficult device use; testicular hypotrophy with no identified cause; previous assisted reproductive technology (ART) pathway.
Before starting this method, it is therefore advisable to consult a healthcare professional informed about CTRT (cf. user resources): interview, physical examination (inspection and palpation of the testicles), prescription of a spermogram (SPG) and a spermocytogram.
DESIGN AND INNOVATION
WHY DEVELOP CONTRACEPTIVE BOXER SHORTS?
In France, over 10,000 men are already practicing thermal contraception using homemade devices.
A contraceptive boxer could be a simple, reliable, comfortable, and ready-to-use solution that replaces your usual underwear and changes nothing in your daily life, except for contraception.
WHY A BOXER RATHER THAN ANOTHER TYPE OF UNDERWEAR?
In our opinion, the boxer is the most common and comfortable underwear for daily wear. Its contemporary design also allows for a combination of style, precise support (for contraception), and discretion.
HOW IS THE 37.1 DEGREE BOXER DESIGNED AND TESTED?
The 37.1 boxer briefs from 37 degrés are made from polyamide and elastane, materials frequently used for sports underwear, combining mechanical elasticity, long-term resistance, comfort, and softness. Their technical design combines reliable and targeted compression for increased support effectiveness, and absolute comfort for users.
Based on the initial proof of concept developed by co-founder Gaëlle Burcklé, a patent was filed, and R&D work was then carried out to define the final form of the device, which was tested by several independent testers. A second patent was filed for the final form.
WHAT IS THE STATUS OF THE 37-DEGREE BOXER 37.1 DEVELOPMENT?
The contraceptive boxer short, the 37.1 by 37 degrees, is currently under development.
We currently market the 37.0 boxer short, which ensures testicular ascent.
To evolve it from 37.0 to 37.1 and make it a contraceptive medical device, we need to launch preclinical and clinical trials, with the aim of testing the contraceptive effect and safety of the device on a large scale, and then obtaining CE marking, proof of its effectiveness as a reliable contraceptive medical device, and authorized for marketing on the European market.
We anticipate the start of clinical trials in early 2027, and the marketing of the medical device in mid-2029.
HOW TO SUPPORT THE 37 DEGREES PROJECT?
In several ways!
You can purchase the exploration boxer to test it, offer it to others (a gift card is also available), and provide us with feedback through our feedback form regarding its comfort, support, and design to help us improve it.
You can also supplement your purchase with a donation to support the project's development or contact us if you wish to invest and participate in its deployment.
Finally, don't hesitate to talk about the project around you, follow us on social media (Instagram, TikTok, LinkedIn) and encourage your friends and family to do the same. This is also an opportunity to talk about contraception and start fighting stereotypes by showing that men, too, can take charge of their fertility!
THE BOXER 37.0
WHAT IS THE BOXER 37.0 FOR?
The 37.0 boxer shorts are a product for bodily and intimate exploration, a wellness product.
They allow you to discover your body, to experience your intimacy differently, to try out testicular thermoregulation, and to become familiar with this physical practice.
The 37.0 boxer shorts are exclusively intended for bodily exploration and should not be used for any other purpose. In particular, they have no medical, therapeutic, diagnostic, or contraceptive purpose.
Wearing these boxer shorts is also a way to support the 37 Degrees project and participate in the dissemination of this knowledge.
WHY THIS PRICE?
We want a fair and accessible price. The price set today reflects the many stages and design elements, as well as the complexity of technical research and development, materials, production, testing and validation phases, preclinical and clinical trials, European certification (CE), but also the commitment to a still emerging contraceptive innovation that aims to be sustainable, effective and stylish.
IS WEARING BOXERS PAINFUL, UNCOMFORTABLE, OR RISKY?
The 37 degrees 37.0 boxer shorts have been designed for comfortable wear. They respect everyone's anatomy and morphology. Their various features ensure ease in all circumstances: a wide waistband for enhanced support, a discreet and intuitive pocket for ease of use and testicular lift, textiles that combine comfort, performance, breathability and durability, an adjustable internal ring that supports, without ever constricting.
The 37.0 boxer shorts may require a short adaptation period, but their wear should not be painful in any way. We recommend not wearing them for more than a few hours during the first few days. Soon, you will be perfectly accustomed to their presence, just like your socks.
WHEN TO WEAR THE 37 DEGREES 37.0 BOXER SHORTS?
The 37.0 boxer shorts are designed for occasional wear, as part of a journey of bodily exploration. They allow you to discover your body, your intimacy, and to experience testicular retraction.
CAN YOU EXERCISE WHILE WEARING THE 37.0 BOXERS FROM 37 DEGREES?
Yes, if the activity remains comfortable and does not create uncomfortable chafing or pressure points. It is essential to listen to your body and your sensations.
The 37.0 boxer shorts from 37 degrees can even be particularly comfortable during sports sessions, as they hold the testicles close to the body, preventing them from bouncing around.
HOW TO CHOOSE THE RIGHT SIZE 37 DEGREES BOXER 37.0?
Refer to our size guide chart and choose according to your low hip, hip, and thigh measurements.
For greater accuracy, take your measurements directly on your skin using a tape measure:
- Low hip circumference: at the level of the upper edge of the pelvis (the one you can feel forming an angle when you run your hands over your hips, at the front of the body)
- Hip circumference: at the widest point (on the fullest part of the hips, including your buttocks)
- Thigh circumference: at the fullest point, without squeezing (≈ 2 cm below the crotch)
Tip: you can also measure the elastic of your favorite boxer shorts laid flat, then add 9 to 10 cm to estimate your low hip circumference; remember to multiply this measurement by 2.
Between two sizes? Choose the smaller one for good support.
Well-fitting boxer shorts should be comfortable, offer good support, and not restrict your movement.
HOW TO SET THE BOXER 37.0 TO 37 DEGREES?
- Put on the 37.1 boxer shorts like classic underwear.
- Open the pouch located at the front of the boxer shorts to access the internal trapezoid opening.
- Loosen the stopper to widen the opening as much as possible.
- Using your hands, grasp the penis and gently pass it through the opening.
- Without manipulating the testicles, gently grasp the skin of the scrotum and pass it through the opening: the testicles naturally rise towards the pubis, the empty scrotum appears below the penis.
- Check that the opening correctly surrounds the base of the penis and the empty scrotum. The opening and the internal part should be pressed firmly against the body, while the penis and scrotum are contained in the boxer's pouch.
- Adjust the cord using the stopper to adapt the opening to the circumference of the penis and scrotum. If necessary, tie a knot above the stopper to prevent any slipping.
- Pull up the boxer shorts to tighten the internal part: it should not be loose.
- Regularly check the position of the testicles throughout the day and readjust the device if necessary.
IS THE 37-DEGREE BOXER 37.0 VISIBLE UNDER CLOTHING?
No, the 37.0 boxer shorts from 37 degrees, in addition to being reliable, comfortable and stylish, are also discreet, with no added bulk. Under a pair of trousers, they will look just like classic boxer shorts.
The 37 degrees jacquard logo remains discreet while being elegant.
HOW TO MAINTAIN THE 37-DEGREE BOXER 37.0?
Wash the boxer briefs before first use, and after each day of use.
Turn the boxer briefs inside out before each wash.
Wash at a temperature not exceeding 30 °C, in a laundry net.
Do not use bleach.
Do not dry clean.
Do not soak the boxer briefs before or after washing.
Promptly remove the boxer briefs from the washing machine once the cycle is complete.
Do not tumble dry: air dry the boxer briefs, away from a direct heat source (radiator, sun...).
Do not iron.